A good friend died last year and left about 10,000 kits, mostly unstarted and about 200 built models. He left tons of model cars, trucks, motorcycles but also trains, military, boats, stuff he never built. There are also a few hundred high end diecast. My friend is selling them off for the family at about 10 - 15 kits a week. Doing the math, this could cause him to go insane trying to sell them all. At a few shows, he sells a lot, maybe 100-200 kits but that is not much of a dent in the thousands still gathering dust. We have talked about having an auction house sell them but in this area, they get about 5-10% of the value, then take 25% commision, leaving almost nothing for the seller. Last summer I was given several 1/8th and other large scale built models and a few banker boxes (5) of spare 1/8th parts from the collection and it took me a few days to find space for the built models. I am still sorting the parts boxes.
I have been selling at local shows for many years and have started to sell more so my wife doesn't have to deal with them. Lowering the prices helps sell them faster but I don't want to give them away. I also have a paragraph in my will as to who gets what and who doesn't. :) Selling built models is far more difficult than selling kits, started or projects.
Now when I go to a store or show or see a collection online, I am more carefull about what I buy...but I still buy a few pieces. :) I'm not dead yet. :) I still enjoy the hobby and have several projects on the go, who doesn't. It is different being in your 70s than 50s and not enough time to build everything.